One of the primary modes of shipping goods is by a truck pulled trailer. These trailers are equipped with a landing gear assembly that is retracted in a stored position above the ground while the trailer is coupled to the truck. The landing gear assembly allows the trailer to be uncoupled from the truck when necessary. After placing the trailer in a desired location, the operator lowers the landing gear assembly into contact with the ground. Once in contact with the ground, the truck is disengaged from the trailer. Loading the trailer or placing the landing gear assembly in contact with relatively soft ground may affect the trailer height above the ground. When the operator is ready to re-couple the trailer to a truck it may be necessary to extend the landing gear assembly to raise the trailer.
Two speed landing gear assemblies have been developed to allow the operator to more efficiently couple and uncouple trailers from trucks. A high gear mode allows the landing gear assembly to move rapidly between the stored position and the ground. Once in contact with the ground, the low gear mode allows the landing gear assembly to lift the trailer. The operator turns a crank to raise or lower the landing gear assembly. The ratio of crank turns per inch of travel of the landing gear assembly is smaller for the high gear than for the low gear. In other words, the legs will extend more per turn of the crank in high gear than in low gear. Some two speed landing gear assemblies include a gear box attached to one of the legs of the landing gear assembly. An input shaft turns an output shaft via the gears contained in the gear box. The output shaft interacts with the lifting mechanism in both legs of the landing gear assembly to extend or retract the legs. In this configuration, the leg having the gear box functions as a master leg and the other leg functions as a slave leg.
Current landing gear assemblies split the mechanical advantage (created by the gear box) between the two legs. As a result, relatively large forces are placed on the lifting mechanism in each leg and the cross bar between the two legs which affects the service life of the landing gear assembly. Another drawback of current landing gear assemblies is that the operator can only extend and retract the legs in high and low gears from the master leg location. Still another limitation of current landing gear assemblies is that a single set of legs cannot be mounted in the multiple configurations required by the different types of trailers.